This invention relates to drive units for automobiles, and in particular to automobiles having automatic transmissions.
Throughout much of the operational time of a vehicle, in particular a passenger automobile, the engine runs without driving the vehicle. For example, during intermittent short-time stopping of the vehicle, e.g., due to traffic conditions, the engine, with the transmission in neutral, will continue to turn at the idling speed. Also, during deceleration and coasting, not only is the engine not driving the vehicle, but it will itself be driven at a higher speed by the vehicle's forward momentum acting through the wheels of the car and transmission. Such coasting or deceleration occurs not only on driving downhill, but whenever during travel the driver releases the accelerator pedal.
In both operating conditions, deceleration as well as idling, fuel delivered to the engine is wasted inasmuch as it is not utilized to drive the vehicle. In some cases of coasting and deceleration, braking by the engine is desirable for reasons of safety to boost the main foot brake, since the engine is used to dissipate kinetic energy. In cases other than travel down a steep incline, however, the fact that the engine continues to run when not powering the vehicle constitutes an unprofitable utilization of increasingly scarce fuel resources.
Commonly-owned copending U.S. application Ser. No. 191,079, filed Sept. 26, 1980, discloses a drive train for a vehicle having an automatic transmission which utilizes an auxiliary starting motor and an internal combustion engine to eliminate the requirement for a torque converter. A non-combustion type starting motor, preferably electric, is used for the initial acceleration of the vehicle, through the flywheel and the automatic transmission, until a pre-selected rotational flywheel speed or vehicle speed is achieved. At this point, a mechanical clutch is closed thereby connecting the flywheel to the crankshaft of the internal combustion engine and rapidly starting the engine. The internal combustion engine is disconnected in engine-braking and idling phases of operation when the mechanical clutch is opened by a servo-motor which operates as a function of the position of the accelerator pedal. In this prior copending application, however, the internal combustion engine is not always disconnected in all engine-braking and idling phases.
According to the present invention, an improved drive train is provided whereby the internal combustion engine is disconnected in all engine-braking and idling phases to maximize fuel conservation, yet sufficient energy is maintained in the flywheel mass to start the internal combustion engine immediately when the accelerator pedal is depressed.